Railway signaling system



F. H. NICHOLSON 2,268,163 RAILWAY SIGNALING'SYSTEM Filed May 18, 1940 2 Sheets-Sheet 1.

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HIIS ATTORNEY- Dec. 30, 1941. F. H. NICHOLSON RAILWAY SIGNALING SYSTEM 2 Sheets-Sheet 2 Filed May 1s, 1940 I n 0 I N b mw m a T 0 N b m IJAOI. I I m J mv n H m I I m N Kw I K S EQWMfiL I N m m m F av vmfiw hwfiv w I Q N NNNWw I NE N theme of energy of this type.

Patented Dec. 30, 1941 RAILWAY. SIGNALING SYSTEM Frank H. Nicholson, Penn Township, Allegheny County, Pa., assignor to The Union Switch &

Signal Company, Swiss of Pennsylvania vale, Pa., a corporation Application Ma 18, 1940, Serial in. 335,992

13 Claims. (o1. 'i24 -13o) iMy invention relates to railway traflic controlling apparatus of the type employing coded current in the track circuits thereof, and particularly to means for discontinuing operation of highway crossing signals or for controlling other apparatus conditioned upon occupancy of a track section,

One advantage of the use of coded or periodically interrupted current in track circuits is the improved shunting sensitivity which results from If steady uncoded energy is supplied to a track section to discontinue operation of a highway crossing, or to determine occupancy of the track section for, any other purpose, the advantage of It is an object of this invention to provide an improved railway signaling system employing coded or periodically interrupted energy in the track circuits to control the signalsgoverning movement of trains in the trackstretch, and incorporating means for at times employing coded energy in a track section to detect occupancy of; 4

ing signals.

A. further object of the invention isto provide an improved signaling system of the type dethe. section without afiecting the trafiic governscribed, the equipment being arranged so that when coded energy is supplied to a track circuit 'for detection purposes the track relay of the track circuit is disconnected to thereby prevent response of the track relay to the energy supplied for detection purposes.

Another object of the invention is to provide an improved signaling system of thetype described, the equipment being arranged so that whena train enters a track section operation of ahighway crossing signal is initiated, and have ing means for supplying coded energy to the .tr-ack circuit at the entrance end of the sectiontogether with code responsive means at the exit end of the section fordiscontinuing operation of the crossing signal when the train vacates the section.

Afurther object of the invention is to provide in a railway signaling system of the type employing coded or periodically interrupted energy in thetraclr circuits thereof, means for controlling a highway crossing signaLthis means being arranged so that it does not require a code following track relay to respond to uncoded energy.

Another. object of the invention is to provide improved, 1 shunting sensitivity resulting from the use of coded energy is lost as long as steady energy is supplied to the track section.

1 a railway signalingsystem incorporating means for controllinga highway crossing signal, the system being arranged so that failure of line wires employed therein will affect only the crossing signals and will not interfere with the intended operation of the signals governing movement of trains in thetrack stretch. 3

Other objects of the invention and features of novelty will be apparent from the following description taken in connection withthe accompanying drawings.

I shall describe one form of railway signaling system embodying my invention, together with a modification which I may employ, and shall then point out the novel features thereof in 7 claims.

In the drawings:

Fig. 1 is a diagram of a stretch of railroad track equipped with signaling apparatus embodying my invention, and i i Fig. 2 is a diagram showinga modification which I may employ. Referring to the drawings, there is shown therein a stretch of railroad track having track rails I and 2 over which traiiic normally moves in the direction indicated by the arrow, that is from left to right. l

The rails of the track stretch are divided by insulated joints3 into track sections for signalingpurposes. One of the track sections includes an intersection with a highwayand the rails of this section have additional insulated joints 3 therein to divide thesection into an approach 'section B! IT and a clearing section AI'IT to facilitate control of the crossing signals XS which protect theintersection. Portions of two other track sections are shown and are identified as sections IiiT and IZT.

Each of the principal track sections has 10-- cat-ed at the entrance end thereof a wayside signal for indicating to approaching trains the nature of the traffic conditions in advance. As

shown these signals are of the familiar color light type, each having a green or clear lamp G,

#2. yellow or caution lamp Y, and a red or stop lamp R, The wayside signals are desigated IIS and 523 in the drawings.

It is to be understood that the invention is not 9 limited to a system employing this type of signals, however, and that any suitable type of waysignals may be employed. The invention is also applicable to trackstretches which do not have wayside signals, but employ cab signals only.

The rails of each of the track sections for a part of a track circuit to which coded alternating current signal control energy is normally continuously supplied at the exit or leaving end of the section from a current supply device in the form of a track transformer designated IT with an appropriate prefix.

Each of the track circuits includes, in addition, an electroresponsive device in the form of a code following track relay having a winding receiving energy from the rails of the section at a point adjacent the entrance end of the section.

The circuits for supplying energy from the track transformer secondary windings to the rails of the track sections include the usual current limiting reactors 6. q I l r The energy supplied to the track circuits is derived from any suitable source, and may be secondary winding on the transformer IUTI. As hereinafter explained this secondary winding is at times connected with the rails of section Bl IT adjacent the entrance end of the section. The second track circuit also includes an electroresponsive device in the form of a code following track relay N which has a winding which at times is connected through a resonant rectifier unit NRU to the rails of section Bl IT adjacent the exit end of the section.

An interlocking relay XR is provided to control the crossing signals XS, while a slow releasing auxiliary relay M is provided to control the supply of energy to one winding of the interlocking distributed throughout the track stretch by a transmission line, not shown. In the drawings the reference characters BX and CK designate the-terminals of such power'supp y Source, and

' it will be assumed that the energy supplied from fthis source is alternating current of a frequency of 100 cycles per second.

'Ihe signaling system shown in the drawings is of thethr'ee-indication varietyand makes use ot track circuit energy coded at two different frequencies. This coded energy is provided by "code transmitters- CT which interrupt the cir- "-cuits of the associated track transformers a definite number of times a minute according to ,tr afficlor other conditions in advance. In the lustrative form shown each code transmitter CT i sprovided with two circuit making and breaking ----contacts-'15 and [80 which are continuously actuated by a motor or other suitable mechanism attwo different speeds. For purposes of illusfltration it willb'e assumed that these speeds are such-as to provide75 and 180 energy pulses per minute which are separated by periods of equal duration in which no energy is supplied.

The track relays TR maybe of any suitable and 'as shown, are of the direct current efe'ach havinga winding connected to the c'krails of the associated track section through suitable resonant rectifier unit RU shown diagrammatically in the drawings.

The resonant rectifier units RU each comprise a transformer, a capacitor and a reactor so arranged and proportioned as to freely pass the 100 cycle signal control energy, but so as not to pass energy of a different frequency, while a rectifier is incorporated in each unit to convert into direct current the alternating current which is supplied through the unit.

' Each of the track relays has associated therewith a suitable source of direct current, such as a. primary or a storage battery, not shown, the

' terminals of which are designated B and C in the drawings. 7

" Thetrack relay TR at the entrance end of each principal track section has associated therewith decoding means comprising a decoding transformer DT, and auxiliary relays H and J. The

J decoding-means is not a part of this invention,

and any suitable apparatus well known in the art may be employed for this purpose.

V ,-'I 'he track relay AI ITR for the clearing section A l IT hasassociated therewith a front contact repeater relay Al IFSA and a back contact repeater relay Al IBSA.

Theapproach section BI IT is provided with a 7 second or reverse track circuit in addition to the usual or normal trackcircuit. The second track circuit includes asupply device in the form of a relay,and to also control a circuit for supplying energy to'the crossing signals XS. The circuit of the winding of the relay M is controlled by the track relay N so that the relay M is at times energized by current supplied over line wires l5 and I6, and at other times is energized by curreiitflsupplied from the local source of direct current.

iThe track relay Bl lTR'has associated therewith an auxiliary relay P which is energized at itimes by current supplied over the line wires [5 and It.

The equipment is shown in the drawings in the jcondition which it assumes when the track ;'stretch isvacant. At this time energy of 180 code frequency is supplied to the track transformer I2TT by the equipment associated with the'section in. advance of section I2T. This en- ;iergy feeds to the track relay I2TR and produces movement of the track relay contact 2|] to its released positionenergy is supplied to the lower half ofthe transformer primary winding. As a result of alternate energization of the two halves of the transformer primary winding, impulses of energy are induced in the secondary windings 23 and 24, while the track relay contact 2| rectifies .the current supplied from the secondary winding V2% to the winding of the relay I2H. As the winding of the relay I2I-I is energized the contacts of this relay are picked up. I

" As the track relay IZTR is responding to envergy of the 180 code frequency the frequency of the current induced in winding 24 is such that sufficient energy is supplied through the resonant unit IZRUA to the winding of relay I2J to pick w up the relay contact.

As contact 25 of relay 12H and contact 21 of relay [U are picked up the circuit of the green or clear lamp G of signal MS is established, and this lamp is lighted to indicate that there are at least two unoccupied sections in advance of the signal.

As contact 28 of relay IZH is picked up the circuit for supplying energy of the code frequency to the track transformer AHTI' is established, and energy supplied through this 1 transformer feeds to the track relay AI [TR and produces code following operation of the relay. On movement of the track relay contact 30 to itspicked-up position energy is supplied to relay Al IFSA, while on movement of track relay contact 3!] to its released position energy is supplied to relay AHBSA over a circuit which includes front contact 31 of relay AI IFSA. A

snubbing resistor 32 .is connected across the terminals of the winding of-the relay AIIFSA to render the relay contacts slowin releasing, while a snubbing resistor 33 is connected across the terminals of the winding of the relay AI IBSA as long as the contact 3| of relay AIIFSA is picked up. The relays AI IFSA and AI IBSA and the snubbing resistors are selected so that the relay contacts "will remain picked up during the intervals between the supply of impulses of energy to the relay windingswhenr the track relay AI ITR. is responding to coded energy.

At this time, therefore; contact 34 of relay AIIBSA is picked up and establishes a circuit through which energy is supplied tothe primary winding 35 of the track transformer BI ITT when I track relay contact? 35 is in its picked-up position. This circuit is interrupted on release of the track relay contact 35-so that as long as the track relay AIITR is responding to coded energy, the energy supplied to the'track transformer BI I'IT is coded at the same frequency as the energy which is supplied to the relay AI ITR. I The circuit of the secondary winding 38 of the track transformer BI I'II includes in series there-: with the primary winding" 40 of the transformer incorporated in the resonant rectifier unit NRU associated with the relay N. The circuit of the secondary winding M of this transformer'is controlled by contact 42 of relay AIIBSA so that the circuit iscomplete when and only when contact :42 is released. At this time as contact 62 is picked up this circuit is interrupted and energy is not supplied through this resonant unit to the winding of the relay N.

is such that the supply of current from thetrack transformer BI ITT to. the rails of section B! IT is not unduly diminished, while this factor is taken into consideration in selecting the reactor 6. I Accordingly sufficient current is supplied from the transformer BIITT to the rails of section I BIIT to insure proper operation of the track relay BI ITR;

At this time, as contact 43 of relay AI IBSA and contact '44 of relay AI IFSA are picked up,

energy is supplied to the winding 46 of the interlocking relay XR and the armature controlled by this Winding is picked up with the result that contacts 41 and 48 establish connection from the line Wires I and IE to the back contacts of relay N. In addition, contact 49 of the interlocking relay XR is picked up and establishes the circuit which is also controlled by a contact of relay M for supplying energy to the winding 54 of the interlocking relay XR.

The relay N is not energized at thistime as contact 42 of relay AI IBSA interrupts the circuit of the resonant unit NRU associated with the relay N. The contacts 50 and 5| of relay N; therefore, are released and engage their back contactsand establish the circuit to supply energy from the line wires I5 and I6 to auxiliary relay M; At this time energy is supplied to the line wires I5 and It by means associated with relay -BI ITR, as hereinafter explained in detail. I

As the relay M is energized its contacts 52 and the armature controlled by this winding is picked up. i

As both windings of the interlocking relay XR are energized both armatures of the relay are picked up and the crossing signals XS are maintained inactive.

As contact 52 of relay M is picked up one circuit for supplying energy to the crossing signals XS is interrupted, and as contact 49 of the interlockingrelay XR is picked up the other circuit for supplying energy to the crossing signals is interrupted, and, accordingly, the crossing signals are inactive at this time.

As pointed out above energy of the 180 code frequency is supplied to the track relay AIITR, and this relay repeats the supply of energy of this'code frequency to the rails of section BI'IT. Energy supplied to the rails of section B! IT is supplied through the resonant unit BIIRU to the trackrelay BIITR and produces code following operation of this relay.

contact 25 of relay BI IE and contact 21 of relay BI IJ are picked up the circuit of the green or. clear lamp G ofsignal I IS is established, while. as contact 28 of relay BI IH is picked up the circuit for supplying energy of the 180 code frequency to the primary winding of the track transformer IllTT is established. Accordingly impulses of current are induced in the secondary ing 58 is complete only when contact 55 of auxil- I iary relay P is picked up, and as this contact is released at this time energy is not supplied from winding 58 to the rails of section Bl IT.

As. the contacts of relay BI II-I are picked up contacts BI} and 6| establish the circuit to. supply energy from the local source of direct current to the line wires I5 and I6 over which energy is supplied to the Winding of the auxiliary relay M at this time.

Operation of equipment on passage of a train through the track stretch in the normal direction of traffic Whena train moving in the normal direction oftrafiic enters theapproach section Bl IT the track relay Bi ITR is shunted and energy is no longer supplied through the decoding transformer BHDT to relays BIIH and BiIJ and these relays become released.

As a resultof the release of relay BI ill the circuit of the green lamp G of the signal IISis interrupted, and the circuit of the red or stop lamp R is established. On release of the contact 28 of rela BI iI-Ithe circuit for supplying energy of the code frequency is interrupted, while the circuit for supplying energy of the '75 code frequency to the transformer IIJT'I is established,

and energy of this. code frequency .is supplied from .the transformer to the rails of section IUT. On release of relay BI IH contacts 66 and 6| interrupt the supply of energy to the line wires I6 and I6 and establish connection from the line wires I and I6 to auxiliary relay P.

On interruption of the supply of energy to the line wires I5 and I6 the supply ofenergy to the auxiliary relay M is interrupted, and relay lVlI releases and contact 53 interrupts the circuit of the winding 54 of the interlocking relay XR. Accordingly, the armature controlled by this Winding becomes released and contact 62 engages its back contact.

. M is in its released position a circuit is established to, supply energy to the crossing signals X8, and

these signals operate to warn users of the highway of the approach of a train.

'Whenthe train advances far enough in the track stretch to enter the clearing section AI IT,

cuiting the primary winding 36 of the track transformer BI I TT. As the primary winding of the transformer BI ITT is short circuited the impedance of the secondary winding 33 is reduced to a minimum.

On release of contact 44 of relay AI IFSA the circuit of the winding 46 of the interlocking relay XR is interrupted, and the armature controlled by this winding moves towards its released position so that contacts 41, 48 and 49 interrupt the circuits controlled thereby. However, because of the internal construction of the interlocking relay 2m. the armature controlled by winding 46 is prevented from moving all of the Way to its released position since the other armature of the relay is already in its released position.

On release of the contacts 43 and 63 of relay AI IBSA energy is supplied to the line wires I5 and I6 from the source of direct current associ-. ated with relay AI ITR. The circuit for supplying energy to the line wires is complete at this time as contacts 64 and 65, which are controlled by winding 54 of the interlocking relay XR, are released.

When the contacts of the relay AI IESA and of the interlocking relay XR establish connection from the local source of direct current to the line wires I5 and I6, energy is supplied over the line wires I5 and I6 to the auxiliary relay P through the contact 60 and BI of relay BIII-l' which are released at this time.

On the supply of energy to relay P contact 55 of this relay picks up and interrupts the circuit for connecting the track relay BIITR with the rails of section BI IT, and establishes the circuit for supplying energy from the secondary winding 53 of the track transformer IUTT to the rails of section BI IT. 7

As pointed out above at this time, as the track relay BI ITR is not responding to coded energy,

the relay BI IE is not energized and its contact '28 is released so that energy of the 75 code frequency is supplied to the primary winding of the track transformer IIITT, and on establishment of the circuit of thewinding 58 oi'the transformer "I IiTT energy of the 75 code, frequency is supplied to the rails of section BIIT.

From the foregoing'i-t will be seen, that when a train moving in the: normal direction of 'trafiic enters the clearing section AI IT, the contacts of the relay AI IBSA release and interrupt the supply of energy to the rails .of section-BI IT through I the transformer BI ITT, that is, the supply device As contact 52 of auxiliary relay I the electroresponsive device of the of the first track circuit of section BI ITT, while contact 42 of relay AI IBSA establishes the circuit for supplying energy from the rails of section BI IT to thewinding of the relay N, that is, second track circuit of section BII'I'.-,

. In addition, at this timewenerg'y is supplied over the line wires I5 and I6 to the winding of the relay P to pick up this relay. When contact 55 of relay'P is picked up it interrupts the circuit for supplying energy from the rails of section BI IT 1 to the winding of the track relay BI ITR, that is, the electroresponsive device of the first track cir' cuit of section BI IT, and establishes the circuit enters the clearing section TI IT, the supply device and the electroresponsive device of the first track circuit of the approach section B-I IT are both rendered inactivegwhile the devices of the second track circuit of section BIIT are both rendered active and the second track circuit serves to detect when the train vacates the approach section.

As long as any portion of the train remains in the approach section BI IT the energy supplied at the entrance end of the section cannot feed to the relay N at the exit end of the section. However, as soon as therear of the train clears ;the approach section BI IT energy feeds from the entranceend of the section tothe primary winding 40 of the transformer which is included in the resonant rectifier unit NRU associated with the relay N. The circuit of the primary winding 46 includes in series therewith the secondary winding 38 of the track transformer BI ITT, but, as pointed out above, the impedance of this winding is at a minimum at this time since the primary winding 36' of the transformer is short circuited. Accordingly, energy may flow freely in the circuit of the transformer primary winding 46.

At this time contact 42 of relay AI I BSA is released and establishes the circuit of the secondary winding M of the transformer of the resonant unit NRU. The resonant unit NRU includes a capacitor and an inductance which are arranged and proportioned so as-to freely pass the alternating current energy of 100 cycle frequency which is employed in the signalsystem and so as r not to pass energy of different frequencies. This unit also includes a rectifier which converts into direct current the alternating current which is supplied through the unit to the winding of the auxiliary relay N.

It will be seen, therefore, that when the rear of the train clears the approach section B! IT relay N to their picked-up position energy is supplied to the relay M from the local source of energy, while the supply of energy to this relay is interrupted during the released periods of the contacts of the relay N. The relay M is of a I type the contacts of which areslow in releasing with the result that the relay contacts pick up and remain picked up during the intervals between the supply of impulses of energy to the relay.

On picking up of the contact 52 of relay M the circuit for supplying energy to the crossing signals XS is interrupted and operation of the crossing signals is discontinued.

On picking up of the contact 53 of the relay M the circuit for supplying energy to the winding 54 of the interlocking relay XRis not established since this circuit is interrupted by contact 49 of the relay XR. Accordingly, the armature controlled by the winding 54 of the relay XR remains in itsreleased positionand contacts 64 and 65 maintain the circuit for supplying energy to the line wires I5 and I6 so that relay P is energized and its contact 55 is picked up to maintain the circuit for supplying coded energy to the rails of section BI IT.

When the train enters section I2T the track relay for this section is shunted and the signal I2S is conditioned to display its red or stop indication, while the energy supplied to the rails of section AI IT is changed from 180 to '75 code frequency.

When the train advances far enough in the track stretch to vacate section AI IT the energy of 75 code frequency feeds to the track relay AII'IR, and produces code following operation of the relay. As a result energy is supplied to the relays AI IFSA and AI IBSA and these relays pick p.

On picking up of the contacts43 and 63 of re- I lay AIIBSA the supply of energy to the line wires I5 and I6 is cut ofi, while as a result of picking up of contact 44 of relay AI IFSA and of contact 43 of relay Al IBSA the circuit .is established to supply energy to the winding 46 of the interlocking relay XR, so that contacts 47, 48 and n 49 become picked up.

On picking up of contact 42 of relayAI IBSA I the circuit of the resonant rectifier unit NRU is interrupted and energy is no longer supplied through this unit to the winding of the relay N and the contacts of this relay become released I and no longer establish the circuit for supplying energy to the winding of the relay M. However; I

because of the slow releasing characteristic of the relay M the contacts of this relay remain picked up for a time interval andcontact 52 continues to interrupt the circuit for supplying energy to from winding 58 of transformer IOTT to the rails I of section BI IT, and to establish the circuit for supplying energy from the rails of section BI IT to the winding of the track relay BI I'IR.

When contact 34 of relay AIIBSA becomes picked up the circuit is established for supplying impulses of energy to the rails of. section BI IT during the'picked-up periods of contact 35 of track relay AI ITR.

It will be seen, therefore, that when the train vacates the clearing section and the contacts of relay AI IBSA become picked up, the devices of I the second track circuit of section BI IT are rendered inactive, while the devices of the first trackcircuit of section BI IT are rendered active.

The energy which is supplied from transformer BI I TT to the rails of section BI IT feeds to the I track relay BI ITR, and the contacts of this relay respond to coded energy so that energy is supplied through the decoding transformer BI IDT to pick up relay BI IH. As the track relay I BI ITR. is responding to energy of code frequencyinsuflicient energy is supplied through the resonant unit BI IRUA to the relay BI IJ to pick up the contact of this relay.

On picking up of contact 25 of relay BI IH the circuit of the red or stop lamp R of signal .I IS

is interrupted, while the circuit of the yellow or I caution lamp Y is established. 4 On picking up of contact 28 of relay BI I H the energy supplied to the rails of section IGT is changed from 75 to code frequency.

When contacts 60 and 61 of relay BIIH are picked up the relay P is disconnected fromthe 1 line wires I5 and I5, while energy is supplied to the line wires. At this time contacts 41 and 48 of the interlocking relay XR are picked up, and f line wires l5 and I6 to the relay M, and energy is supplied over the'line wires to energize the relay.

picked up the circuit: for supplying energy to the winding 45 =of the interlocking relay XR was established and the contacts 41, 48 and 49 became picked up. Contacts 41 and 48 when picked up establish connection from the linewires I5 and I6 to the relay M, while contact 49 when picked iup completesi the circuit for supplying energy to the'winding 54 of the relay KB. This circuit 1 is complete at this time as contact 53 of relay M is picked up. I

On the supply of energy to the winding 54 of the interlocking relay XR' the armature controlled by this Winding becomes picked up and the relay is restored to its normal condition.

It will be seen that the supply of energy to the winding of the auxiliary relay M is interrupted on picking up of the contact 42 of the relay AI IBSA and resultant release of the contacts of the relay N, while the supply of energy to the winding of the relay M is resumed on picking up of the contacts of the relay BI IH;

The contacts of the'relay BI IH become picked up shortly after code following operation of the a track relay BI ITR. is initiated, while code following operation of the relay BIITR is started as soon as the contacts of the relay AI IBSA become picked up. Accordingly there is only a short interval between the time at which the supply of energy to the relay M is interrupted by release of the contacts of the relay N, and the time at which the contacts of the relay BIIH become picked up to establish a circuit to supply energyto the relay M. The relay M is of a type the contacts of which are slow in releasing, and the relay is selected so that its contacts are slow enough in releasing to remain picked up throughout the interval during which energy is not supplied to the:relay winding when code following operation of the track relay AI ITR is initiated.

As the contacts of the relay M are maintained picked up during the change in the condition of the equipment which. occurs when theclearin'g When the contacts of relay AIIBSA become section AI IT is vacated, contact 52maintains the I circuit of the crossing signals'XS open so that these signals are maintained inoperative at this time.

From the foregoing it will be seen that when a train moving in the normal direction of trafiic enters-the clearing section Al IT coded energy is supplied to the rails of the approach section BI IT adjacent the entrance end of the section, and that there is at the exit end of the approach section code detecting means in the form of a code following relay N and an auxiliary relay M. When the approach section BI IT is vacated coded energy feeds to the code detecting means at the exit end of the approach section and the relay M thereupon operates to discontinue operation of the highway crossing signals.

If while the clearing section AI IT is still occupied a second or following train should enter the approach section BI IT, the track rails of the section will be shunted and coded energy supplied at the entrance end of the section will not reach the code following relay N at the exit end of the section. The contacts of the relay N, therefore, will remain released and energy will not be supplied to the relay M and the contacts of relay M will become released, and will effect operation of the crossing signals XS to warn users of the highway of the approach of the train.

Since coded energy is employed in the approach section to discontinue operation of the crossing signals when a train vacates the section, the shunting sensitivity of the track circuit of this section at this time is the same as when the track stretch is vacant. Accordingly, there is no danger that when a train enters the approach section at a time when energy is supplied to the section for the purpose of preventing operation of crossing signals that the train will fail to shunt the track circuit and thus fail to effect operation of the crossing signals.

It will be seen also that when coded energy is supplied to the rails of the approach section for the purpose of discontinuing operation of the crossing signals, the track relay at the entrance end of'the approach section is disconnected from' the track rails of the section :so that there is no possibilitylthat this relay .will respond to the coded energy which is supplied to the rails of the-section at this time.

The coded energy which is supplied to the rails of the approachsection B'I IT for detection purposes is supplied at the entrance end of the section, but this energy cannot effect operation of the cab signalequipment on locomotives traversing the track stretch. Locomotives provided with this equipment have receivers mounted ahead of the leading pair of wheels and receiving energy inductively from the track rails. When a locomotive with this equipment enters the approach section at a time when coded energy is supplied to the, rails of the section for detection purposes, the wheels and axles of the locomotive shunt the rails of the section at points between the receivers and thesource from which energy is supplied to the rails of the section. Accordingly, energy does not reach theportions of the track rails over which the receivers are located and the receivers will not supply energy to the cab signal apparatus. This apparatus, therefore, will be conditioned to display its most restrictive indication.

The-system provided by this invention is arranged so thatif the line wires I5 and I6 are defective for any reason, only theihighway crossing signals XS will be affected, while the signals governing movement of trains in the track stretch will continue to function in the normal manner. I

If, for example, the line wires I5 and I6 become defective at a time when the track stretch is vacant, energy will not be suppliedover the line wires to the auxiliary relay M, and the contacts of this relay will be released to thereby interrupt the circuit of the winding 54 of the interlocking relay XR. Accordingly, the armature controlled by this winding of the interlocking relay XR. will be released, and, as contact 52 of relay M and contact 62 of the interlocking relay are released, energyis supplied to the crossing signals XS, and these signals are caused to operate even though no train is present in the vicinity. This, however, is a safe condition.

At this time the equipment associated with track relay AI ITR operates in the usual manner and energy of the code frequency is supplied through the track transformer BI ITT to the rails of section BI IT, while the track relay BI ITR responds'to this coded energy and conditions the signal I IS to display its clear indication.

It will be seen, therefore, that failure of the line wires at a time when the track stretch is vacant results in operation of the crossing signals XS, but it does not interfere with the si nals governing movement of trains in the track stretch.

If, while the line wires I5 and I6 are defective, a train moving in the normal direction of traffic enters section BI IT, the track relayBI ITR will be shunted and the signal I IS will display its stop indication, while energy of the 75 code frequency will be supplied to the rails of section I 0T. At this time the contacts of relay BIIH will be released to interrupt the supply of energy to the line wires I5 and I6, and to establish connection from the line wires I5 and I6 to the winding of the relay P. As the line wires are assumed to be defective, cutting off of the supply of energy to these wires is without result since the contacts of relay M are already released.

When the train advances .into section AIIT the track relay AI ITR is shunted and the relays AI IFSA and AI IBSA become released. On release of the contact 34 of relay AIIBSA the supply of energy to the. track transformer BI I TT is cut off, while release of contact 42 establishes the circuit of the resonant unit NRU. Onrelease of contacts .43 and 63 of relay AIIBSA, the circuit for supplying energy to the line wires I5 and I6 'is established, but as these wires are assumed to be defective, energy is not supplied over the line wires to the relay P. Accordingly, the contact 55 of relay P remains released and does not establish the circuit for supplying energy from the winding 58 of transformer IDTT to the rails of section BIIT, while contact 55 maintains the circuit for supplying energy to the winding of the track relay BIITR.

At this time, therefore, the track relays BI ITR and N are both connected to the rails of section BI IT, but the transformers BI I TT and IIJTT are both ineffective to supply energy to the rails of section BI IT, and the contacts of the track relays remain released even after the train vacates sectionBI IT.

As the track relay BIITR is deenergized the signal IIS continues to display its stop indication, and as the relay N is deenergized, energy is not supplied to the winding of relay M and the contacts of this relay remain released and maintain the circuit for supplying energy to the crossing signals XS. Accordingly, operation of the crossing signals is not discontinued when the train clears section BI IT.

When the train advances far enough to clear section AIIT, energy of the 75 code frequency feeds to the relay AI ITR, and this relay operates to supply energy to the relays AI IFSA and AIIBSA. On picking up of relay AI IBSA the circuit of the resonant unit NRU is interrupted, while the circuit for supplying energy through the transformer BIITT to the rails of section BIIT is established. Accordingly, energy feeds 1 to the track relay BI ITR and this relay conditions the signal I IS to display its caution indication.

From the foregoing it Will be seen that failure of the line wires does not interfere with operation of the signals governing movement of trains in the track stretch, but that the crossing signals are caused to operate continuously instead of only on the approach of a train. This, however, is a safe condition.

The system shown in Fig. 1 is arranged to employ coded current in the second track circuit of the approach section B! IT. This is the preferred arrangement, but it is possible to employ steady energy in this track circuit, and Fig. 2 is a diagram showing this modification;

Construction and operation of modification shown in Fig. 2 The modification shown in Fig. 2 is the same as that shown in Fig. 1, except as hereinafter specifically pointed out, and the same reference characters are employed to identify the appara tus in Fig. 2 as are employed for the corresponding elements of the system shown in Fig. 1.

The single element direct current code following track relay N employed in the system shownin Fig. 1 is not employed in the system shown in Fig. 2. Instead a two element alternating current track relay NA is employed. This relay has two windings, one of which is constantly energized from the source of alternating current signal control energy. The other winding 39 of the relay NA is connected in series with the secondary winding 38 of the track transformer BIITT, and is thereby connected across the rails of the approach section BI VI.

The contacts 5!! and 5| of relay NA control the circuit of the Winding of the relay Min substantially the same manner as in. the system shown in Fig. 1.

The track transformer IIZTT in the modification shown in Fig. 2, does not have a secondary winding. for supplying energy to the rails of sectionBI IT. Instead a separate transformer TTA is employed for this purpose The primary winding I0 of this transformer is constantly energized from the source of alternating current signal control, energy. The secondary winding I2 of this transformer is at times connected across the rails of section BIIT over a circuit which includes front contact 55 of relay P, while contact 55 of relay P also controls .the circuit of the track relay BIITR.

The operation of the modification shown in Fig; 2 is substantially the same as that shown in result that the relays AI IFSA' and AI IBSA are energized. Accordingly, during the picked-up periods of the track relay contact 35 energy is supplied to the primary winding 35 of the track transformer BIITT so thatenergy is supplied from the transformer secondary winding 38 to the rails of section BI IT over the circuit which includes in series therewith the winding 39 of the relay NA.

The relay NA is of a type the contacts of which will becomepicked up only when the instantanei that when energy is supplied from the transformer to the rails of section BI IT, the instantaneous polarity of the current in the two windings of the relay NA is such that the relay contacts do not become picked up. Accordingly,

contacts 50 and 5! remain released and maintain the circuit over which energy is supplied to the winding of relay M from the line wires I5 and I6.

At this time both windings of the interlocking relay XR are energized, as explained in connection with the system shown in Fig. 1, and the crossing signals XS are maintained inactive. addition, the relay P is deenergized so that the winding of the track relayBI ITR is connected across the rails of section BIIT, while the circuit of the secondary winding I2 of the transformer TTA'is interrupted so that energy is not supplied by this transformer to the rails of section BI IT. The track relay BI ITR. responds to coded energy and causes the signal IIS to display its.

clear indication.

When a train traveling in the normal direction of traffic enters the approach section BI IT the track relay BI ITR is shunted and the signal I IS is caused to display its stop indication, while the I relay BI IH releases and interrupts the supply of energy to the line wires I5 and It and establish connection from the line wires I5 and IE to winding of the relay P.

On interruption of the supply of energy to the line wires I5 and I6 the contacts of relay M 138-.

come released, thereby interrupting the circuit of I the winding 54 of the interlocking relay XR,

and initiating operation of the crossing signals XS to warn users of the highway of the approach of a train.

When the train advances into the clearing sec- 1 tion Al IT the track relay Al I TB is shunted, and

the contacts 43 and 63 of relay AI IBSA become released to establish the circuit for supplying energy to the line wires I5 and I5 and thus to the relay P. Accordingly, the Contact 55 of this relay becomes picked up to interrupt the circuit of the track relay BI ITR, and to establish the circuit for connecting the secondary winding 12 of transformer TTA across the rails of section BIIT. Steady uncoded energy is thereupon supplied from the transformer TTA to the rails of l section BIIT, and when the train vacates the NA, the instantaneous polarity of the impulses of energy supplied to the two windings of the relay is suchthat the relaypicks up and estab lishes a circuit to supply energy tothe winding of the relay M. The contacts of relay M thereupon become picked up, and contact 52 interrupts the supply, of energy to the crossing. signals the XS so that operation of these signals is discontinued.

When the train advances ,farenough in the track stretch to vacate section AIIT the track relay AI ITR responds to coded energy and supplies, current to relays Al IFSA and Al IBSA.

When the contacts of relay AHBSA become picked up the circuit for supplying energy to the line wires l and I6 is interrupted. -In addition, energy is supplied to the winding 46 of the interlocking relay XR, and the circuit for supplying energy to the primary winding 36 of the track transformer Bl ITT is established.

On interruption of the supply of energy to the line Wires I5 and IS the relay P is deenergized,

and its contact 55 becomes released to interrupt the circuit for supplying steady energy from the transformer TT'A .to the rails of section BIIT, and to establish the circuit for supplying energy from the rails of section Bl IT to the winding of the relay BI ITR.

On interruption of the supply of energy from the transformer TTA to the rails of section Bil IT the contacts of relay NA become released and interrupt the supply of energy to relay M. However, because of the slow releasing characteristic of the relay M the contacts of this relay remain picked up until energy is supplied to the relay winding over the line wires. Accordingly, contact 52' interrupts the circuit for supplying energy tothe crossing signals XS, and these signals ,do not operate during this change in the condition and this relaypicks up to establish the circuit for supplying energy over the line wires l5 and It to the relay M, and the contacts of this relay are thereafter maintained picked up.

1 In the event the line wires I5 and I6 are defective for any reason, the modification shown in Fig.2 operates in such a mannerthat only the highway crossing signals are affected, while the signals governing movement of trains in the track stretch continue to function in the intended manner..

While the invention has been illustrated and described in connection with the control of highway crossing'signals, the system is not limited to use in this manner, but may be employed wherever it is desired to detect occupancy of'a track circuit.

Although I have herein shown and described only two forms of railway signaling system embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a section of railway track, a first supply means for at times supplying coded energy to the rails of said section adjacent the exit .end of the section, a second supply means ,for at times supplying coded energy to the rails of said section adjacent the entrance end of the trafllc conditions in the adjacent section in advance of said section and effective when such adjacent section in advance is vacant to condition the first supply means to supply energy to the rails of said section, to render the second supply means ineffective to supply energy to the rails of said section, to render the first code responsive device responsive to coded energy sup plied to the rails of said section and to render, the'second code responsive device non-responsive to coded energy supplied to the rails of said section, said relay responsive to traffic conditions-in said adjacent section in advance of said section being effective when such adjacent section in advance is occupied to condition the second supply means to supply energy to the rails of said section, to render the first supply.

means ineffective to supply energy to the rails of saidsection, to render the first code responsive device non-responsive to coded energy supplied. to the rails of said section, and to render the second code responsive device responsive to coded energy supplied to the rails of said section, and indication means controlled jointly by said first and second code responsive devices.

2. In combination, a section of railway track, a first supply means for at times supplying coded energy to the rails of said section adjacent the exit end of the section, a second supply means for at times supplying coded energy to the rails of said section adjacent the entrance end of the section, a first code responsive device having a winding at times connected across the rails of said section adjacent the entrance end of the section, a second code responsive device having a winding at times connected across the rails of said section adjacent the exit end of the section, a relay responsive to traffic conditions in the adjacent section in advance of said section and effective when said adjacent section in advance is vacant to condition the first supply means to establish the circuit to connect the winding of the first code responsive device across the rails of said section, to render the second supply means ineffective to supply energy to the rails of said section, and to interrupt the circuit for connecting the second code responsive device across the rails of said section, said relay responsive to traffic conditions in said adjacent section in advance of said section being effective when said adjacent section in advance is occupied to interrupt the circuit for connecting the winding of the first code responsive device across the rails of said section, to establish the circuit connecting the winding of the second code responsive device across the rails of said section, to render the first supply means ineffective to supply energy to the rails of said section, and to condition the second supply means to supply energy to the rails of said section, and indication means controlled jointly by said first and second code responsive devices.

3. In combination, a section of railway track, a first supply means for at times supplying coded energy tothe rails of said section adjacent the exit" end of the section, a second supply means for at times supplying coded energy to the rails of said section adjacent the entrance end of the section, a first code responsive device having a winding'to which energy is supplied from the rails of said section adjacent the entrance end of the=section,-a second'code responsive device having a winding to which energy is supplied from the rails of said section adjacentthe exit end of the'section, a relay responsive to trafiic conditions in the adjacent section in advance of said section and effective when said adjacent section in advance is vacant to condition the first supply means to supply energy to the rails of said section, to render the second supplymeans ineffective to supply energy tothe rails of said section, to render the first code responsive device responsive to coded energy supplied to the rails of said section, and to render the second ply energy to the rails of said section, to render the first code responsive device non-responsive tocodedenergy supplied to the rails of said section and to render the second code responsive device responsive to coded energy supplied to the rails of said section, an auxiliary relay,

means responsive to code following operation of the first code responsive device for supplying energy to the Winding of said auxiliary relay, means responsive to code following operation of the second code responsive device for also supplying energy to the winding of said auxiliary relay, and indication means controlled by said auxiliary relay.

4. In combination, a section of railroad track, a first track circuit for said track section comprising a first supply meansfor supplying coded energy to the rails of said section adjacent the exit end of the section and a first code responsive device having a winding to which energy may be supplied from the rails of said section adjacent the entrance end of the section, a second track circuit for said track section comprising a second supply means for supplying coded energy to the rails of, said section adjacent the entrance end of the section and a second code responsive device having a winding to which energy may be supplied from the rails of said section adjacentthe exit end of the section, a relay responsive to traffic conditions in the adjacent section in advance of said section and effective when said adjacent section in advance is vacant to render only the first track circuit operative and eflective when said adjacent section in advance is occupied to render only the second trackcircuit operative, and indication means controlled jointly by said first and second code responsive devices. 4

5. In combination, a section of railroad track, a firsttrack circuit for said section comprising means for supplying energy to the rails of the section adjacent the exit end of the section and an electroresponsive device having a winding to which energy is supplied from therails of the section adjacent the entrance end of the section, a second track circuit for said section comprising means for supplying energy'to the rails of said section adjacent the entrance end of thesection and an electroresponsive device having a Winding to which energy is supplied from the rails of the section adjacent the exit endof the section, a relay responsive to trafiic conditions in the adjacent section in advance of said section and effective when said adjacent section in ad- Vance is vacant to render only the first track circuit operative and effective when said'adjacent sectionin advance is'occupied to render only the: second track circuit operative, a pair of linewires substantially coextensive with said track section,

an auxiliary relay located adjacent the exit end of the section, means governed by the electroresponsive device of the first track circuit for supplying energy to the winding of said auxiliary relay over said line wires, and indication means i controlled jointly by said auxiliary relay and by theelectroresponsive device of the second track circuit.

6. In combination, a stretch of railroad track having adjoining forward and rearward track sections, a first track circuit for the rearward section comprising a first supply means for supplying energy to the section rails adjacent the exit end of the section and a first electroresponsive device havinga winding to which energy is supplied from the track rails adjacent the entrance end of the section, a second track circuit for the rearward section comprising a second supply means for supplying energy to the section rails adjacent the entrance end of the section and a second electroresponsive device having a winding to which energy is supplied from the track rails adjacent the exit end of the section, a first auxiliary relay located adjacentthe exit end of the rearward section, a second auxiliary relay located adjacent the entrance end of the rearward section and operative when and only when energized to condition the second supply means to supply energy to the rails of said rearward section, a pair of line wires substantially coextensive with said rearward section, means governed by traflic conditions in the forward section forsupplying energy over said line wires to the second auxiliary relay, said means being effective to supply energy to said second auxiliary relay when said forward section is occupied, means governed by the first electroresponsive device for supply ing energy over said line wires to the first auxiliary relay, and indication means controlled jointly by the first auxiliary relay and the second electroresponsive device.

7.In combination, a stretch of railroad track having adjoining forward and rearward track sections, a first track circuit for the rearward section comprising a first supply means for supplyend of the section, a second track circuit for the rearward section comprising a second supply means for supplying energy to the section rails adjacent the entrance end of the section and a second electroresponsive device having a winding to which energy is supplied from the track rails adjacent the exit end of the section, a first auxiliary relay located adjacent the exit end of the rearward section, a second auxiliary relay located adjacent the entrance end of the rearward section and operative when and only whenenergized to condition the second supply means to supply energy to the rails of said rearward section, said second auxiliary relay being operative when energized to prevent energy to besupplied from the rearward section rails to the'winding of the first electroresponsive device, a pair of line wires substantially coextensive with said rearward section, means operative when and only when the first electroresponsive device is supplied with energy to establish connection to supply energy over the line wires to the winding of the first auxiliary relay, said means being operative when and only whenthe first electroresponsive device through which energy may be supplied over the line-wires to the winding of the second auxiliary relay, means governed by traffic conditions in the forward section for supplying energy over the line wires to the winding of the second auxiliary relay, said means being effective to supply energy to said second auxiliary relay when said forward section is occupied, and indication means controlled jointly by the first auxiliary relay and the second electroresponsive device.

8. In combination, a stretch of railroad track having adjoining forward and rearward sections, a first and a second track circuit for the rearward section, each of said track circuits comprising a supply devicefor supplying energy to the section rails at one end of the section and an electroresponsive device having a winding receiving energy from the section rails at the other end of the section, the supply device of the first track circuit being located at the exit end of the section and the supply device of the second track circuit being located at the entrance end of the section, means responsive to traffic conditions in said forward section, said means being effective when the forward section is vacant to establish connection between the devices of the first track circuit and the rails of the rearward track section, said means being effective when the forward-section is occupied to establish connection between the devices of the second track circuit and the rails of said rearward section, an auxiliary relay located adjacent the exit end of the rearward section, means governed by the supply of energy to the electroresponsive device of the first track circuit for supplying energy to the winding of said auxiliary relay, and indication means controlled jointly by said auxiliary relay and the electroresponsive device of said second track circuit.

9. In combination, a stretch of railway track having adjoining forward and rearward track sections, a first and a second track circuit for said rearward section, each of said track. circuits comprising a supply device for supplying energy to the section rails at one end of the section and an electroresponsive device having a winding to which energy may be supplied from the section rails at the other end of the section, the supply device of the first track circuit being located at the exit end of the section and the supply device of the second track circuit being located at the entrance end of the section, a line circuit substantially coextensive with said rearward section, a first auxiliary relay located at the exit end of the rearward section and a second auxiliary relay at the entrance end of the rearward section, means responsive to and operative on the supply of energy to the electroresponsive device of the first track circuit to supply energy over the line circuit to the winding of the first auxiliary relay, means governed by trafiic conditions in the forward section for supplying energy over the line circuit to the winding of the second auxiliary relay, said means being effective to supply energy to said second auxiliary relay only when said forward section is occupied, said second auxiliary relay controlling the supply device of the second track circuit of said rearward section'in such manner that said device is efiective to supply energy to the section rails when and only when the second auxiliary relay is energized, and indication means controlled jointly by said first auxiliary relay and the electroresponsive device of the second track circuit of said rearward section. I

10. In combination, a stretch of railway track having adjoining forward and rearward'track sections, a first and a second track circuit for said rearward section, each of saidtrack circuits comprising a supply device for supplying energy to the section rails at one end of, the section and an electroresponsive device having a winding to which energy may be supplied from the section rails at the other end of the section, the supply device of the first track circuit being located at the exit end of the section and the supply device of the second track circuit being located at the entrance end of the section, a first auxiliary relay located at the exit end of the rearward section and a second auxiliary relay located at the entrance end of the rearward section, means operative on the supply of energy to the electroresponsive device of the first track circuit for said rearward section to supply energy to the winding of the first auxiliary relay, means governed by trafiic conditions in theforward section for supplying energy to the winding of the second auxiliary relay, said means being effective to supply energy to said second auxiliary relay only when said forward section is occupied, said second auxiliary relay controlling the supply device of the second track circuit of said rearward section in such manner that said device is effective to supply energy to the section rails when and only when said second auxiliary relay is energized, and indication means controlled jointly by said first auxiliary relay and by the electroresponsive device of the second track circuit of said rearward section.

11. In combination, a stretch of railway track having adjoining forward and rearward track sections, a first and a second track'circuit for said rearward section, each of said track circuits comprising a supply device for supplying energy to the section rails at one end of the section and an electroresponsive device having a winding to which energy may be supplied from the section rails at the other end of the section, the supply device of the first track circuit being located at the exit end of the section and the supply device of the second track circuit beinglocated at the entrance end of the section, a first and a second auxiliary relay, means responsive to and operative on the supply of energy to the electroresponsive device of the first track circuit for supplying energy to the first auxiliary relay, means governed by trafiic conditions in the forward section for supplying energy to the winding of the second auxiliary relay, said means being effective to supply energy to said second auxiliary relay only when said forward section is occupied, said second auxiliary relay controlling the supply device of the second track circuit and being operative when and only when energized to condition said device to supply energy to the rails of said rearward section, and indication means controlled jointly by said first auxiliary relay and the electroresponsive device of the second track circuit of said rearward section.

12. In combination, a stretch of railway track having adjoining forward and rearward track sections, a first and a second track circuit for said rearward section, each of said track circuits comprising a supply device for supplying energy to the section rails at one end of the section and device of the first track circuit being located at the exit end of the section and the supply device of the second track circuit being located at the entrance end of the section, means responsive to occupancy of said forward section for controlling the track circuits of the rearward section, said means being effective when said forward section is vacant to render the first track circuit operative and to render the second track circuit inoperative, saidmeans being also effective when the forward section is occupied to render the first iary relay, and indication means controlled joint- 1y by said auxiliary relay and the electroresponsive device of the second track circuit for said rearward section. t 13. In combination, a stretch of railway track having adjoining forward and rearward track sections, a first and a second track circuit for saidrearward section, each of said track circuits comprising a supply device for supplying energy which energyv may be supplied from the section rails at the other end of the section, the supply device of the first track circuit being located at the exit end of the section and the supply device of the second track circuit being located at the entrance end of the section, means responsive,

to occupancy of said forward section for controlling the track circuits of the rearward section, said means being effective when said forward section is vacant to render the first track circuit operative and to render the second track circuit inoperative, said means being also effective when the forward section is occupied to render the first track circuit inoperative and the second track circuit operative, an auxiliary relay, means controlled by the electroresponsive device of the first track circuit for supplying energy to said auxiliary relay, means controlled by the electroresponsive device of the second track circuit for also supplying energy to said auxiliary relay, and indication means controlled by said auxiliary relay.

' FRANK H. NICHOLSON. 

